1. Pressures from activities
  2. Outer Hebrides

Outer Hebrides

The tables in this section reflect the output of the workshop (October 2019) when the pressures from human activities were assessed for the period 2014 to 2018 for the region. The summary text below the tables elaborates on some of the points that were made at the workshop.
This pressure assessment uses the FeAST classification which includes two abrasion pressures: surface abrasion & sub-surface abrasion. Some expert groups combined these as a single pressure "surface & sub-surface abrasion" whilst others focussed on using surface abrasion alone, hence there is a slight difference in handling for some regions.
The ranking of the pressures in terms of impact is a relative exercise within each region, and is not a statement of their absolute impact. Detailed comparison between regions on the basis of these relative pressure assessments is therefore not advisable.

Image of the Outer Hebrides Scottish Marine Region

Main pressures identified

Priority [1] Pressure (FeAST classification) [2] Main healthy and biologically diverse components affected [3] Main contributing FeAST activity /activities to pressure [4] Associated productive assessments [5]
1 Removal of target species (including lethal)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
  • Fishing - Dive fisheries (not including hydraulic dredging) (HF, MIS)
  • Fishing - Line fishing (hand and mechanized line and longlining) (LHP, LHM, LL, LLS)
  • Fishing - Pelagic trawling & purse seining (OTM, PTM, TM, PS, PS1, PS2)
  • Fishing - Recreational Fishing
  • Fishing - Scallop dredging (DRB)
  • Seaweed harvesting
2 Removal of non-target species (including lethal)
  • Aquaculture - Finfish
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
  • Fishing - Intertidal fishing (e.g. bait digging but not bivalves).
  • Fishing - Line fishing (hand and mechanized line and longlining) (LHP, LHM, LL, LLS)
  • Fishing - Pelagic trawling & purse seining (OTM, PTM, TM, PS, PS1, PS2)
  • Fishing - Recreational Fishing
  • Fishing - Scallop dredging (DRB)
  • Seaweed harvesting
3 Surface abrasion
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Creeling and potting (FPO)
  • Fishing - Scallop dredging (DRB)
4 Sub-surface abrasion/penetration
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Scallop dredging (DRB)
5 Underwater noise
  • Aquaculture - Finfish
  • Military activities – Sea surface activity
  • Military activities – Sonar use
  • Shipping

Footnotes:
• This pressure assessment uses the FeAST classification which includes two abrasion pressures: surface abrasion and sub-surface abrasion. Some expert groups combined these as a single pressure - Surface & sub-surface abrasion - whilst others focussed on using surface abrasion alone, hence there is a slight difference in handling for some regions.
• The ordering of entries in columns 3, 4 and 5 is not in any particular priority. There isn’t a 1:1 relationship between the entries in columns 3 and 4.
• Where aquaculture is identified as a source of noise pressure, this is due to the potential presence of Acoustic Deterrent Devices (ADDs) in this retrospective (2014-2018) pressure assessment.
• Column 4, FAO gear type added for clarity to fishing types. The gear type annotated next to the FeAST Activity is the International Standard Statistical Classification of Fishing Gear (ISSCFG). This was originally adopted during the 10th Session of the Coordinating Working Party on Fishery Statistics (CWP) (July 1980).
• Note the possibility of terrestrial influence for litter.

Other pressures identified

Barrier to species movement
De-oxygenation
Death or injury by collision below water
Emergence regime changes - local
Genetic modification and translocation of indigenous species
Hydrocarbon & PAH contamination. (Includes those priority substances listed in Annex II of Directive 2008/105/EC).
Introduction of microbial pathogens (disease), viruses or parasites
Introduction or spread of non-indigenous species and translocations (competition)
Nitrogen and phosphorus enrichment
Organic enrichment
Physical change (to another seabed type)
Physical loss (to land or freshwater habitat)
Synthetic compound contamination (inc. pesticides, antifoulants, pharmaceuticals). Includes those priority substances listed in Annex II of Directive 2008/105/EC.
Visual disturbance (behaviour)

Footnote: the ordering of entries is alphabetical and there is no prioritisation between the pressures.

Summary from workshop

The Outer Hebrides exhibits many similarities to the West Highlands region, but with weaker fresh water influence from terrestrial run-off. Though not a top five pressure, there is much uncertainty in terms of collision risk. Mainly driven by commercial vessel activity in this region. This region is of great apparent significance to basking sharks. Numerous seal haul out sites exist; small cetaceans (porpoises/dolphins) are regularly observed. The region is also important for minke whales, and other whale species.

 

1 Removal of target species (lethal): bottom otter trawling and pair trawls; creeling and potting; dive fisheries; line fishing (hand and mechanised longlining); pelagic trawling and purse seining; recreational fishing; scallop dredging; seaweed harvesting.

 

2 Removal of non-target species: bottom otter trawling and pair trawls; line fishing (hand and mechanized longlining); pelagic trawling and purse seining; recreational fishing; scallop dredging; intertidal fishing e.g. bait digging; creeling and potting; finfish culture (shooting of seals under license); seaweed harvesting.

 

3 Surface abrasion: bottom otter trawling and pair trawls; creeling and potting; line fishing (hand and mechanized longlining); scallop dredging.

 

4 Sub-surface abrasion: bottom otter trawling and pair trawls; scallop dredging.

 

5 Underwater noise: military (sonar use for military purposes); sea surface military activity (vessel noise); finfish culture; shipping.